Increase In Inhibition Activity Research Articles

Binding of phosphorylated peptides and inhibition of their interaction with disease‐relevant human proteins by synthetic metal‐chelate receptors

The modulation of biological signal transduction pathways by masking phosphorylated amino acid residues represents a viable route toward pharmacologic protein regulation. Binding of phosphorylated amino acid residues has been achieved with synthetic metal-chelate receptors. The affinity and selectivity of such receptors can be enhanced if combined with a second binding site. We demonstrate this principle with a series of synthetic ditopic metal-chelate receptors, which were synthesized and investigated for their binding affinity to phosphorylated short peptides under conditions of physiological pH. The compounds showing highest affinity were subsequently used to inhibit the interaction of the human STAT1 protein to a peptide derived from the interferon-gamma receptor, and between the checkpoint kinase Chk2 and its preferred binding motif. Two of the investigated ditopic synthetic receptors show a significant increase in inhibition activity. The results show that regulation of protein function by binding to phosphorylated amino acids is possible. The introduction of additional binding sites into the synthetic receptors increases their affinity, but the flexibility of the structures investigated so far prohibited stringent amino acid sequence selectivity in peptide binding.

The influence of γ-irradiation on some biological activities and electrophoresis patterns of wheat grain albumin fraction

Water-soluble proteins were extracted from irradiated wheat grain for the purpose of assaying biological activities, reducing sugars content and SDS–PAGE electrophoresis. The differences between samples after γ-irradiation were tested by analysis of variance at the level of significance ( P ⩽ 0.05). Ionising radiation (0.05–10 kGy) caused an increase in the activity of endogenous amylases, statistically significant at doses of 5 and 10 kGy ( P ⩽ 0.05), which was well correlated with the highest extractable protein content. γ-Irradiation of wheat grain at a dose of 0.05 kGy caused an increase of inhibition activity against Sitophilus granarius L. α-Amylase, whereas there was a decrease at 10 kGy ( P ⩽ 0.05). On the other hand, grain irradiated by 0.5 and 1 kGy doses showed a significant increase in inhibition activity against α-amylase of Tribolium confusum Duv. ( P ⩽ 0.05) while at the remaining doses the inhibition activity was on the same level as the control grain. Decrease of Ephesitia kuehniella Zell. α-amylase was observed only at 5 kGy radiation dose ( P ⩽ 0.05). At the remaining doses this activity was comparable to non-irradiated grain. The highest increase of antiamylolytic activity against human saliva α-amylase was noted in albumin proteins of wheat grain treated by γ-radiation doses >0.5 kGy while there were decreases at radiation doses <0.5 kGy ( P ⩽ 0.05). The increase of inhibition activity against hog pancreas α-amylase was noted at radiation doses 0.1 kGy ( P ⩽ 0.05). γ-Radiation doses of 0.05, 0.5 and 1 kGy caused an increase of the antitryptic activity while 10 kGy decreased this activity ( P ⩽ 0.05). SDS–PAGE electrophoresis patterns of albumin sample at 0.1 kGy showed 15 proteins while in the control sample only 11 bands were found. Among studied wheat albumins, the lower protein bands 5 and 8 were detected in wheat grain samples irradiated by 10 and 0.5 kGy, respectively. The differences in inhibitor activities and electrophoretic protein bands of wheat albumin from γ-irradiated wheat grain give additional evidence that these proteinaceous inhibitors against enzymes studied are different in nature.

Time-Dependent Inhibition of Prostaglandins Synthesis by Nonsteroidal Antiinflammatory Drugs; Time-Dependent Alteration of Inhibitory Effect and Characteristics of its Active Site

The characteristics of the tlme-dependency of nonsteroidal antiinflammatory drugs (NSAIDs) and their active sites in inhibiting cyclooxygenase activity were investigated using bovine seminal vesicle microsomal fraction. The Hill's coefficients of the inhibition curve of most NSAIDs were approximately 1.0, except for some drugs which had Hill's coefficients that were obviously more than 1.0. The values for indomethacin, diclofenac and flurbiprofen were approximately 1.5, 1.7 and 2.0, respectively. A time-dependent cyclooxygenase inhibiting effect was observed only with the NSAIDs in the group which had Hill's coefficients that were significantly more than 1.0. A time-dependent increase in inhibiting activity of these drugs was observed by the change in the inhibition curve. Time-dependently, the Hill's coefficient of the curve of the NSAIDs approached 1.0 from more than 1.0. With this change, the shift of the curve to the left was also observed time-dependently. These changes in the curve were no longer seen when the Hill's coefficient dropped to 1.0. These time-dependent effects were protected by salicylic acid, which did not have any effect on cyclooxygenase activity in vitro, in a dose-dependent manner. These results suggested that the two classes of NSAIDs, time-dependent and non-time-dependent, are clearly differentiated by the slope of the inhibition curve of NSAIDs. Furthermore, the present results indicate that the degree of time-dependence of the NSAIDs depends on the Hill's coefficient of the inhibition curve, and the value is important for the potency of the cyclooxygenase inhibition, in addition to the affinity for the catalytic site of the enzyme.

PHENOLICS FROM LARIX NEEDLES. VI. EFFECT OF SHORT-DAY TREATMENT

A short-day (SD) photoperiod of 3 to 7 days was critical for delay in budding of defoliated seedlings. Both growth-stimulating and growth-inhibiting substances were present in Larix needle extracts. SD treatment induced a decrease of stimulation and an increase in inhibiting activity. The concentration of one of the main flavonoids, a vitexin derivative, was significantly decreased in SD needle extracts.